(1) Field of the Invention
The present invention relates to a voltage sensing device and more particularly to a means for accurately sensing the load-induced AC voltage drop across the remote, load end of a long two-conductor cable from the proximal end thereof.
(2) Description of the Prior Art
Often, long cables are required to feed electrical power to a remote load. The ensuing voltage drop across the load in these instances can be substantially different from the source voltage applied at the input end of the cable. This voltage difference is the result of IR drop in the cable due to cable resistance. In addition, where the cable length exceeds a small fraction of a wavelength at the applied frequency, such voltage difference is also contributed to by standing waves which occur when the load impedance and the characteristic cable impedance differ. There are many applications, however, where it is desirable to accurately know the voltage drop across a remote load but the load end of the cable is not readily accessible, such as when an underwater sound projector is the electrical load. In these cases in particular it is difficult to obtain an accurate measurement of the load voltage due to the IR drop not being precisely known or more importantly because standing waves are present and the cable and/or load impedance are not accurately known. In the latter case the load voltage may be equal to, greater than or less than the voltage applied at the cable input end.